Stress Measurements in Thin Zirconia Films At 300°C Using Synchrotron Radiation

Abstract

Zirconium alloys used as cladding materials for nuclear fuel oxidise into zirconia during their stay in the reactor. The zirconia formed develops high compressive stresses because the molar volume of the oxide is greater than that of the metal. For a better understanding of the oxidation behaviour of these alloys, stress measurements on thin oxide films at the working temperature of reactor are necessary. They have been performed at 300°C by means of X-ray diffraction techniques on metal sheets previously oxidized in an autoclave. The experiment has been done on the multi-techniques goniometer of the IF beam line at ESRF by coupling the sin²(Ψ) method, grazing incidence configuration and sample heating. Stress tensor and tetragonal zirconia content of oxide layers ranging from 0.5 to 2.5 µm have been determined for two different alloys: zircaloy-4 and Zr-1%Nb. A comparison between 300°C and room temperature results has been made.